Pleistocene

The skeleton of the Hundsheim rhinoceros, Stephanorhinus hundsheimensis. From Kahlke and Kaiser, 2010. In any given environment, it might be expected that a generalized or unspecialized species might be less prone to extinction than one which depends upon a narrow temperature range, a peculiar kind of food, or other aspect of natural history which is key to its survival. An herbivorous mammal which can subsist on a variety of grasses, leaves, and other plant foods, for example, may be more likely to survive an ecological disruption than a species tied to foliage which might die back during…
The nearly complete skeleton of a Steller's sea cow (Hydrodamalis gigas) - it is missing bones from the wrist and hand. From Woodward, 1885. It did not take long for the last remaining population of Steller's sea cow to be driven into extinction. Discovered by the German naturalist Georg Steller around the Bering Sea's Commander Islands in 1741, this enormous and peculiar sirenian became an easy target for Russian hunters. By 1768, it was gone. (The marine mammal would not be scientifically described until 1780, and today it is formally known as Hydrodamalis gigas.) Yet, despite the clear…
A golden-mantled ground squirrel (Spermophilus lateralis), photographed in Bryce Canyon National Park, Utah. Though abundant at the Samwell Cave Popcorn Dome, California site during the Late Pleistocene, its numbers in the area decline at the beginning of the present Holocene epoch. "One of the penalties of an ecological education", the naturalist Aldo Leopold once wrote, "is that one lives alone in a world of wounds." Few knew this better than he did. Despite becoming a celebrated advocate of wilderness for its own sake during the early twentieth century, Leopold began his career by…
The skeleton of an elk-moose (Cervalces scotti), photographed at the New Jersey State Museum.
A muskox (Ovibos moschatus), photographed in Alaska. From Flickr user drurydrama. Of all the mass extinctions that have occurred during earth's history, among the most hotly debated is the one which wiped out mammoths, saber-toothed cats, giant ground sloths, and the other peculiar members of the Pleistocene megafauna around 12,000 years ago. It was not the most severe mass extinction, not by a long shot, but unlike the end-Cretaceous catastrophe 65 million years ago there is no single "smoking gun" that can account for the pattern of extinction. Instead the Pleistocene mass extinction…
Did our ancestors exterminate the woolly mammoth? Well, sort of. According to a new study, humans only delivered a killing blow to a species that had already been driven to the brink of extinction by changing climates. Corralled into a tiny range by habitat loss, the diminished mammoth population became particularly vulnerable to the spears of hunters. We just kicked them while they were down. The woolly mammoth first walked the earth about 300,000 years ago during the Pleistocene period. They were well adapted to survive in the dry and cold habitat known as the 'steppe-tundra'. Despite the…